Atmos. Chem. Phys. Atmospheric Chemistry and Physics, vol. 9 (2009) pp. 1723-1734
This paper presents a climatology and trends of tropospheric ozone in the Southwestern Indian Ocean (Re - union Island) and South Africa (Irene and Johannesburg) . This study is based on a multi - instrumental dataset : PTU - O 3 ozonesondes , DIAL LIDAR and MOZAIC airborne instru - mentation . The seasonal profiles of tropospheric ozone at Reunion Island have been calculated from two different data sets : ozonesondes and LIDAR . The two climatological profiles are similar , except in austral summer when the LIDAR profiles show greater values in the free troposphere , and in the up - per troposphere when the LIDAR profiles show lower values during all seasons . These results show that the climatological value of LIDAR profiles must be discussed with care since LIDAR measurements can be performed only under clear sky conditions , and the upper limit of the profile depends on the signal strength . In addition , linear trends have been calculated from ozonesonde data at Reunion and Irene . Considering the whole tropospheric column , the trend is slightly positive for Reunion , and more clearly positive for Irene . Trend calcula - tions have also been made separating the troposphere into Correspondence to : G . Clain (gaelle . clain@univ - reunion . fr) three layers , and separating the dataset into seasons . Re - sults show that the positive trend for Irene is governed by the lower layer that is affected by industrial pollution and biomass burning . On the contrary , for Reunion Island , the strongest trends are observed in the upper troposphere , and in winter when stratosphere - troposphere exchange is more frequently expected .
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